Delhi Gets BS-VI Fuel: But Is Your Old Car Ready for It?

Except for some imported cars, none of the cars made in India can reap the emissions benefits of BS-VI fuel.

Fuel retailers across Delhi and the National Capital Region have apparently been refilling their supplies with BS-VI compliant fuel (both petrol and diesel). Most pumps of state-run oil retailers will start supplying only Bharat Stage VI compliant fuel from 1 April 2018, while the rest of the country will shift to BS-VI compliant fuel from April 2019.

However, no car maker, except for Mercedes Benz, is ready with BS-VI compliant engines at the moment. All the cars currently on sale in India comply with BS-IV (or Euro-IV) emissions standards.

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That brings up the question – if you are going to be using BS-VI fuel in your BS-IV or older car, what are the effects it will have on your engine and on the environment?

What’s the Difference Between BS-IV and BS-VI Fuel?

The main change in fuel quality from BS-IV to BS-VI is in the amount of sulphur content in the fuel – both petrol and diesel. Sulphur is used as a lubricant within the fuel, which helps in better combustion as it keeps pumps and fuel injectors healthy. However, sulphur is also responsible for higher particulate matter emissions (PM 2.5 and PM 10) – the bugbear of diesel vehicles.

While selected metro cities in India shifted to BS IV emissions norms in 2010, the rest of the country only shifted to BS-IV norms only in April 2017.

With BS-IV fuel sulphur content in both petrol and diesel is limited to 50 parts per million (50 ppm). In earlier BS-III fuel, it was 350 ppm for diesel and 150 ppm for petrol. With BS-VI fuel coming in, sulphur content drops to a maximum of 10 ppm.

So what happens to older engines not built for BS-VI fuel? Will there be issues?

Effect of BS-VI Fuel on BS-IV Engines

Since BS-VI fuel has lower sulphur content, there has been concern about the wear and tear on mechanical parts, especially the fuel pump and the fuel injectors. Fuel injectors are responsible for atomising fuel and spraying it into the cylinder for combustion (spark ignition in the case of petrol and high compression ignition in the case of diesel).

In reality, using BS-VI fuel in a BS-IV compliant car won’t make much of a difference in the short term. The slight loss in lubricity can be countered by using fuel additives.

With BS-VI fuel, there will be a slight improvement in emissions as particulate matter emissions (PM 2.5 and PM10) will drop by at least 50 percent.

For the full impact of BS-VI fuel to be felt, one needs a BS-VI compliant car, which has additional parts such as a diesel particulate filter (DPF) and urea injection (to reduce nitrous oxide emissions). Without this, the effect on the environment will be minimal.

However, if you have a car that is pre-BS-IV (that is BS-III or older), using BS-VI fuel could be even more detrimental to engine life. It could cause trouble with injection pumps, oil seals and injectors, leading to higher wear and tear and consequently higher emissions. Hence, the government is adamant on getting rid of these cars and hence a car scrapping policy is in the works.